Heretofore, as one of the wide angle zoom lenses with a zoom ratio of about 2.5, a two-group type zoom lens formed of a first lens group having a negative refractive power and a second lens group having a positive refractive power, disposed in order from the object side in which zooming is performed by moving the first and the second lens groups in optical axis directions is known. This type of zoom lens is favorably used for small video cameras and the like.
For example, U.S. Pat. No. 5,877,901 describes a two-group type zoom lens in which the first lens group is formed of four lenses, i.e., a negative lens (lens having a negative refractive power), a negative lens, a negative lens, and a positive lens (lens having a positive refractive power), disposed in order from the object side (Example 5). Further, U.S. Pat. No. 5,844,724 describes a zoom lens having a similar lens configuration to that described above (Example 2).
Still further, U.S. Patent Application Publication No. 20030234985 describes a two-group type zoom lens in which the first lens group is formed of four lenses, i.e., a negative lens, a positive lens, a negative lens, and a positive lens, disposed in order from the object side (Example 1).
Further, U.S. Patent Application Publication No. 20060077565 describes a two-group type zoom lens in which the first lens group is formed of four lenses, i.e., a negative lens, a negative lens, a negative lens, and a positive lens, disposed in order from the object side and the second lens group is also formed of four lenses, i.e., a positive lens, a positive lens, a negative lens, and a positive lens, disposed in order from the object side (Example 1).
Still further, U.S. Pat. No. 6,169,635 describes a two-group type zoom lens in which the first lens group is formed of four lenses, i.e., a negative lens, a positive lens, a negative lens, and a positive lens, disposed in order from the object side and the second lens group is also formed of four lenses, i.e., a positive lens, a positive lens, a negative lens, and a positive lens, disposed in order from the object side (Example 4).